In 2026, Grand Seiko unveiled the "Evolution 9 Collection Spring Drive UFA Ushio 300 Diver," a watch with a convenient 40.8mm diameter for everyday wear, equipped with the ultra-high-precision Cal.9RB1 movement from their "Spring Drive UFA" series. Watch writer Shinichi Sato will explore this new diver's watch, focusing on four key topics.
Automatic Spring Drive movement (Cal. 9RB1). 33 jewels. Power reserve of approximately 72 hours. Bright titanium case (40.8mm diameter, 12.9mm thickness). 300m water resistance for air diving. 165 yen (tax included).
Text by Shinichi Sato
[Article published on January 7, 2026]
A deep dive into Grand Seiko's latest diver's watch, the "Ushio 300 Diver."
This time, we'll be taking a deep dive into the latest diver's watch added to the Grand Seiko lineup, the "Evolution 9 Collection Spring Drive UFA Ushio 300 Diver" (hereinafter, Ushio 300 Diver). The highlights of this model are: ① a 40.8mm diameter case size and a lightweight bright titanium exterior; ② the inclusion of the ultra-high-precision Spring Drive UFA; ③ a dial with depth themed on the ocean currents surrounding the Japanese archipelago; and ④ a newly adopted buckle with a length adjustment function. Watch writer Shinichi Sato, who has had the opportunity to handle the actual watch, will explain the high level of craftsmanship and appeal of this model.
① 40.8mm diameter case size and lightweight bright titanium exterior
The case of this model, excluding the crown, has a diameter of 40.8mm and a thickness of 12.9mm, making it a size that is easy to use as a daily-wear diver's watch. Considering that the standard for modern informal watches is around 40mm in diameter, this model has a silhouette that will be familiar to many people. Furthermore, the case of the previously released "Evolution 9 Collection" Ref. SLGA015 had a diameter of 43.8mm and a thickness of 13.8mm, so this model is about 3mm more compact in diameter and about 1mm more compact in thickness.
I had previously thought that while previous Grand Seiko diver's watches, including the Ref. SLGA015, were too large for Japanese people, they were well-received in Europe and America, where many users have thicker wrists. Considering Grand Seiko's popularity in Europe and America, this is probably not wrong. However, at Watches & Wonders Geneva 2026, where this model was unveiled, there were apparently many overseas fans who welcomed the size of the Ushio 300 Diver. This episode suggests that this new era of Grand Seiko diver's watches will gain popularity among a wide range of people.
The exterior, including the case and bracelet, is made of lightweight bright titanium. The matte texture is based on a fine hairline finish, with polished edges, giving it a refined and elegant look. When worn, the size and fit were excellent, matching well with shirts, and the lightweight construction made it remarkably comfortable to wear.
② Equipped with the ultra-high-precision Spring Drive UFA Cal.9RB1.
This watch is equipped with the ultra-high-precision Spring Drive UFA Cal.9RB1, boasting an annual deviation of ±20 seconds. "UFA" stands for Ultra Fine Accuracy, and the name is derived from "VFA (Very Fine Adjusted)," which was given to the high-precision model released in 1969. The Cal.9RB1 is a non-date version of the Cal.9RB2 announced last year, with the power reserve indicator moved to the dial.
The Cal.9RB1 incorporates a Spring Drive control IC with added temperature compensation and a carefully selected, aged quartz movement, along with a speed regulator switch. Its appeal lies in its extremely high level of refinement, which enhances the overall accuracy of the system while making it easy to maintain.
③ A dial with depth, themed around the ocean currents surrounding the Japanese archipelago.
The newly announced blue and green dial models both feature stamping and coloring themed around the ocean currents surrounding Japan. The stamped patterns are organic, representing the waves and currents on the ocean surface, and feature a gradient coloring that is darker around the edges and lighter in the center.
The blue color represents the vast ocean shimmering with light, while the green is inspired by the clarity of the shallow waters of a clear sea. Both are muted, sophisticated colors with a slightly matte finish, giving them a calm and refined look. When light hits them, the transparency becomes more pronounced, and the embossed pattern becomes visible. The shadows created by the embossed pattern add expression and a sense of depth. This change in appearance is something you should definitely see in person.
The bezel is made of highly scratch-resistant ceramic and is color-matched to the dial. Its matte finish is a distinctive feature, matching the texture of the dial and exterior, and contributing to the watch's understated appearance.
Automatic Spring Drive movement (Cal. 9RB1). 33 jewels. Power reserve of approximately 72 hours. Bright titanium case (40.8mm diameter, 12.9mm thickness). 300m water resistance for air diving. 165 yen (tax included).
④ Newly adopted buckle with length adjustment function
Finally, what caught my attention was the newly adopted buckle with a length adjustment function. It achieves the length adjustment mechanism while ensuring the robustness required for a diver's watch. Furthermore, it features a compact and thin design that is comparable to buckles without an adjustment function.
The bracelet lifts up at the center of the buckle, and the length can be adjusted by releasing the locking mechanism that appears there, so it seems unlikely that the length will change unintentionally. Like the bracelet, it is made of bright titanium, so it is lightweight and comfortable to wear.
Be sure to check out the highly refined Ushio 300 Diver at a store near you.
The Ushio 300 Diver is a practical and aesthetically pleasing model, featuring a size and lightweight construction that makes it easy for daily use, a Spring Drive UFA movement incorporating Grand Seiko's technical expertise, a calm design incorporating Japanese scenery, and a newly developed, highly convenient buckle. Through this in-depth examination, I was captivated by the high level of craftsmanship of this model, and I confidently recommend it as a model that will provide ample satisfaction to any user who owns it.
The lightweight construction, comfortable fit, and dial that changes its appearance depending on the light are all points that can only be appreciated by actually holding the watch in your hands, so readers considering a purchase should definitely check it out in a store.
